Butterfly Caterpillar Silk

All caterpillars produce silk. Some moth caterpillars even spin silk cocoons; however, only one species, the “silkworm,” Bombyx mori, produces the radiant silk fiber used in garments. Unlike other moths, it weaves its cocoon from a single, continuous strand that is manufactured into silk thread. Native to China, silkworms have been domesticated for over 5,000 years and are extinct in the wild. As a domesticated animal, it has been altered by humans and can no longer fly to find a mate. And they have been improved using GMO technology to splice the genes for the much stronger spider silk into their genome.

Local Silk Moths

Over 2,300 species of Silk Moths exist in the world. We have five beautiful native species in the Kansas City area. The pale green Luna Moth reigns as the favorite. We also see Cecropia, the largest native moth in North America. Polyphemus, Imperials and Io moths are large and colorful but elusive. Many attempts have been made to raise the Chinese silkworm on our native mulberry tree. Countless experiments have endeavored to fuse the shorter silk fibers of our native species into continuous strands. All these efforts have failed. However, you can buy Chinese silkworms on the internet to keep as pets if you have a nearby mulberry tree.

Butterfly Silk

Both moth and butterfly caterpillars have spinnerets, which are modified salivary glands located on their lower jaw. They spit out the liquid silk which hardens on contact with air to form strands of fibroin protein. Butterfly caterpillars do not make cocoons like moth caterpillars but are equally skilled at using silk for many applications in their lives. When a butterfly caterpillar chooses its pupation site, it spits a silk pad from its mouth, then it flips around to attach to the silk pad by hooks on its butt. The caterpillar may also spit out silken slings as additional safety lines.

Silk Carpets, Tailors and Tentmakers

Some species of butterfly caterpillars spin a silk carpet to sit on after they hatch from their egg. They rest immobile all day, enlarging the silk carpet as they grow. This tactic protects the caterpillar from hungry birds, which are drawn to movement, changes in position or holes in a leaf. At night after birds have gone to bed, the caterpillar crawls all over the tree munching on leaves far away from its carpet. And by dawn it returns to its silk carpet on an unblemished leaf.

Many caterpillars hide from birds by stitching the edges of a hostplant leaf into a nest with silk thread. Some species frequently upgrade to larger leaves as they grow. Other species stitch multiple leaves together to accommodate their growth. The caterpillar leaves the nest at night to feed, but returns by dawn. If you want to find the caterpillar, look for these leaf nests, which are referred to as “tacos” or “burritos” depending on its shape.

Rather than sewing leaves together, the Painted Lady caterpillar weaves a canopy tent entirely of silk with the caterpillar clearly visible inside. Unlike other nest making caterpillars, the Painted Lady caterpillar makes only one nest, which it enlarges as it grows rather than crawling away to sew larger leaves into a new nest.

Summary

Humans use silk for fashion while caterpillars use silk for function. Survival in this cruel world requires many tactics and silk-making is one of a caterpillar’s most valuable tools. Eastern Tiger Swallowtail caterpillars spin a silk carpet as their daytime resting spot.

Painted Ladies spin a silk canopy between host plant leaves such as this Hollyhock.

The white silk pad for attachment is clearly visible above this Monarch Chrysalis.

LENORA LARSON Butterfly Maven

A Marais des Cygnes Master Gardener, Lenora is a member of the Idalia Butterfly Society and Kansas Native Plant Society. She gardens in the clay soil and cruel winds of Paola, KS. She may be contacted at lenora.longlips@gmail.com.